296 



SCIENCE 



[Vol. V., No. 114. 



by the sound arising from shaking rods within it, 

 Mr. Andrew Haddow, the engineer, lowered four 

 eight-inch bar-magnets (placed end to end, with the 

 south pole down) into the bore. The north pole of a 

 compass-needle in the mine moved first to the west, 

 and then to the east, of magnetic north, as the mag- 

 nets were lowered, indicating that the magnets were 

 to the westward of the compass. While the heading 

 was being enlarged in this direction, Mr. Haddow 

 experimented by passing a magnet around the com- 

 pass, and drawing a series of curves for positions of 

 the magnet, which produced different angular deflec- 

 tions of the needle. The compass was then placed 

 successively at two different points in the heading, 

 and the deflections caused by the magnets in the 

 bore-hole were noted, — at one point 3f°, at the 

 other 6£°. The two points were then marked on 

 the plan of the mine, a tracing of the magnetic 

 curves just referred to was placed over each point, 

 and the intersection of the curves corresponding to 

 these deflections was noted. Upon excavating to the 

 point thus indicated, the bore was found, being about 

 eight feet from the true vertical. 



In a second case, in Australia, the diamond drill, 

 in going down three hundred and seventy feet, had 

 deviated beyond sensible magnetic influence, and the 

 search by underground mining was continued for 

 nearly twelve months without success. Mr. E. F. 

 Macgeorge then employed glass phials partly filled 

 with melted gelatine, and having a compass-needle 

 in a lower connected bulb of the phial. When these 

 were carefully lowered in the bore to different depths, 

 and the gelatine congealed, the needle would become 

 fixed in the magnetic north, and the surface of the 

 gelatine would be horizontal. These two indications, 

 when the phial was withdrawn, showed the inclina- 

 tion and magnetic bearing of the bore-hole at that 

 point; and a sufficient number of observations at 

 convenient depths permitted the erratic bore-hole to 

 be completely mapped from top to bottom. This 

 map showed a deviation of nearly forty feet at three 

 hundred and seventy feet down (the point so long 

 searched for), and of between seventy and eighty 

 feet at the full depth of five hundred feet. A drift 

 straight for the indicated spot found the lost bore 

 thirty-seven feet and a half away from its proper 

 place, and the bottom was found seventy-five feet 

 astray. This device has since been perfected and 

 patented. 



FISHING-INTERESTS IN HUDSON BAY. 



The chief commercial value of this district un- 

 doubtedly lies in its immense fishing-interests, if we 

 include in that term whaling and sealing. 



American whaling-vessels have for more than a 

 quarter of a century been conducting a very profit- 

 able fishery in Roe's Welcome, a large basin in the 

 north-western portion of Hudson Bay. The vessels 

 usually leave New England in July, and reach Marble 

 Island in September, where they winter, one or two 

 every season, and occasionally more. Sawing out of 

 the ice in the following June, and pressing northward 



as fast as the ice will permit, they fish until about 

 the first of September, unless sooner loaded, and 

 then sail for home. During the eleven years preced- 

 ing 1874, about fifty voyages are known to have been 

 made; and the returns give an average of $27,420 per 

 voyage, which shows a large margin of profit to the 

 small sailing-vessels usually engaged in the trade. 

 It is estimated that the aggregate value of oil and 

 whalebone already obtained is about two and a quar- 

 ter million dollars, and every thing points to a large 

 extension of the industry. 



The porpoise-fishery is extensively carried on by 

 the Hudson-Bay company; the fish, as they are popu- 

 larly called, being held in check by means of trap- 

 nets on flats in coves where the tide rises ten or 

 fifteen feet, and left high and dry when the water 

 recedes. Last year the company secured nearly 

 two hundred in one tide at Churchill, and a much 

 larger number at Ungava Bay. The blubber weighs 

 from two hundred and fifty to four hundred pounds, 

 and is very rich in the finest of oil. Formerly the 

 blubber was exported ; but the company has estab- 

 lished extensive refineries at several of its northern 

 stations, and now ships the oil in casks. 



The company also carries on a walrus-hunt, send- 

 ing two sloops annually from Churchill to two very 

 productive walrus-grounds north of Marble Island, 

 where they have never failed to obtain full cargoes 

 of blubber, ivory, and hides in a few weeks, besides 

 carrying on a valuable trade in oil, ivory, musk-ox, 

 and other skins, with the northern Eskimo. 



During the exploring-steamer Neptune's visit to 

 Stupart's Bay, the Eskimo were living on the harp- 

 seal (Phoca groenlandica Linne), and had in their 

 possession skins of a good many harbor and square- 

 flipper seals (Phoca vitulina Linne, and Erignathus 

 barbatus Fabricius), seals of all kinds being abun- 

 dant. 



The Hudson-Bay company has a steamer, the 

 Diana, plying between London and Ungava Bay di- 

 rect, fitted up with refrigerating apparatus, and en- 

 gaged solely in conveying salmon fresh to the London 

 market. Last year's cargo is reported to have real- 

 ized eighteen thousand dollars. Nearly every stream 

 contains both salmon and trout in vast quantities, 

 chiefly where the salt and fresh waters mingle. 



Cod abound in the vicinity of Chudleigh, though 

 not up to the present time found in Hudson Bay. 

 Newfoundland schooners even now work as far north 

 as Nachvak, and seem to be going farther each year. 

 The cod, though good, are not equal to those of the 

 Banks. While the Neptune was at Port Burwell, 

 both in going and on returning, the anchorage 

 teemed with cod, which were taken in great numbers 

 by jigging from the ship's deck. 



THE DRAINAGE SYSTEM OF BRAZIL.* 



The hydrographic features of Brazil are to a cer- 

 tain extent determined by the orographic system, and 

 by the distribution of mountains and plains described 



1 From the Rio News. 



